Pallet exchanging apparatus for machine tool

ABSTRACT

A pallet exchanging apparatus for machine tool used for exchanging the pallet loaded with the machined workpieces with the pallet loaded with the workpieces to be machined. The pallet exchanging apparatus has a transmission device for shifting the pallet between a work position on a table of the machine tool and a waiting position for exchanging the pallets. The transmission device is driven either by the movement of the table or the movement of the driving mechanism for the table and is adapted to output the rotational movement. The output of the transmission is used for driving a speed-up device. The speed-up device is adapted to move the pallet linearly with higher speed and larger stroke than those of the linear movement of the table.

This is a division, of application Serial No. 085,033, filed Aug. 12,1987 now U.S. Pat. No. 4,799,582.

FIELD OF THE INVENTION AND RELATED ART STATEMENT

The present invention relates to an apparatus for exchanging palletsused for a machine tool.

A pallet exchanging apparatus used for machine tool is well known, theapparatus being adapted to shift the pallet between the first positionwhere the pallet loaded with already machined work pieces are to beexchanged with the pallet loaded with workpieces to be machined and thesecond position where the workpiece or workpieces on the pallet aremachined. The second position can be selected on the table of themachine tool for machining said workpieces.

In the pallet exchanging apparatus according to a prior art, such ashifting device is used wherein a chain 50 is secured to the pallet 1 asshown in FIG. 9, the sprockets 51, 52 with the chain 50 wound thereaboutare rotatably supported by a frame 53 to which the rod 55 of a cylinder54 is fixedly mounted, and a part of the chain 50 is secured to theframe 56 of the pallet exchanging apparatus to which the cylinder 54 isfixed. Operation of the cylinder 54 causes the rod 55 to be projectedand retracted, so that the sprockets 51, 52 are moved and at this timerotation of the sprockets 51, 52 causes the pallet 1 to be reciprocatedbetween the second position on the table as shown by a solid line andthe first position as shown by a phantom line.

It is also to be noted from FIG. 10 that such a construction is alsoemployed as pins 58 adapted to engage with the engaging part 57 providedon the pallet 1 are attached to the chain 59, the chain 59 is woundaround the sprockets 60, 61 and the sprocket 61 is driven by the motor62 so that the pallet 1 may be reciprocated between the second positionon the table as shown by a solid line and the second position shown by aphantom line.

According to the above-explained pallet exchanging apparatus of a priorart, there have been such problems as a separate driving source isrequired for exchanging pallets, energy consumption is considerable,attachment as well as detachment of pallets are cumbersome and alsoexchanging the pallet loaded with machined workpieces with the palletwith the workpieces still to be machined requires a lot of work.

OBJECT AND SUMMARY OF THE INVENTION

The present invention has it as an object to provide a pallet exchangingapparatus which will eliminate the problems as above mentionedpertaining to a prior art and has simplified the constitution thereof.

The above-mentioned object has been attained by the present inventionwhich provides a transmission device adapted to output the rotary motionfrom the rotary or linear motion provided by the driving means or thelinear motion of the table itself in the machine tool, and a speed-updevice adapted to transmit the rotary motion provided by thetransmission device to the pallet as higher speed and a larger strokelinear motion than those of the linear motion of the table.

Although the transmission device and the speed-up device are describedas separate units in the claims of a relevant patent, they should not belimited to such separate units and they may be constituted as one unitand any device may be included in the device what is claimed as long asthey are capable of shifting the pallets at a higher speed and a- largerstroke than those of a table based on the linear motion of the table.

When pallets are to be exchanged, as the table is moved, a higher speedlinear motion may be obtained as the output of the speed-up devicethrough rotary motion taken out of the transmission device or directlyfrom the linear motion of the table. Since the output part of thespeed-up device is coupled to a pallet, the pallet may be shifted at ahigher speed than the shifting speed of the table and with largerstrokes than that of the table. When the table has shifted to aspecified position the pallet which has been loaded on the table will bemoved to a first position or a waiting position lying outside of thetable.

According to the present invention, since movement of the table itselfof a machine tool or movement of a driving device for shifting the tableare utilized to cause the pallets to be moved in relation to the tablefor exchanging the pallets, no separate driving device will be required,thereby simplifying the mechanism, reducing the cost and makingsynchronization of the movement of pallets with that of the table easierand more accurate. Since the motor for the machine tool in itself may beused so that the speed of exchanging the pallets which will be suitablefor the particular size of workpieces may be selected. In this way, ithas become unnecessary to provide an unnecessarily large motor for aworkpiece exchanging device for a large workpiece which may not befrequently used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the plan view of the machine tool according to the presentinvention,

FIG. 2 is the left side elevation of a major part in FIG. 1,

FIG. 3 is the sectional view showing a part of the gear train of atransmission device,

FIG. 4 is the plan view as seen from the right side elevation in FIG. 3,

FIG. 5 is the view corresponding to FIG. 2 showing a further embodiment,

FIG. 6 is the view corresponding to FIG. 2 showing still anotherembodiment,

FIG. 7 is the right side elevation of the transmission device and thepart of a speed-up device in FIG. 6,

FIG. 8 is the view corresponding to FIG. 2, showing a still furtherembodiment, and

FIG. 9 and FIG. 10 are explanatory views of the driving device for aknown pallet exchanging device.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention will now be explained in detail with reference tothe embodiment shown in the accompanying drawings.

In FIG. 1 and FIG. 2, workpiece or workpieces attached to a pallet 3 aremachined by the tool supported by a main spindle head 2 of a machinetool 1. The pallet 3 is attached on a table 4. In order that the pallet3 be movable leftwardly and rightwardly (X-axis direction) and upwardlyand downwardly (Y-axis direction) as viewed in FIG. 1, the table 4 has asaddle 6 adapted to be movably guided by rails 5 in the Y axis directionon the bed of the machine tool 1 and a clamp base 8 adapted to beslidably guided by the rails 7 in the X axis direction provided at thesaddle 6.

The saddle 6 may be reciprocably moved by such a driving means not shownas a motor with a screw or hydraulic cylinder or the like. The clampbase 8 is reciprocably moved by a ball-screw 9 (which may be a normalscrew otherwise) driven by a motor not shown mounted on the saddle 6 anda nut 10 engaged with the ball-screw 9 and secured to the clamp base 8.

In the clamp base 8, there is provided a cylinder portion 11 in which apiston 12 is caused to move vertically by one hydraulic pressure. Aclamp guide plate 13 is secured or integrally formed on the piston 12.The clamp guide plate 13 is so formed that it may be inserted in a guidegroove 14 formed on the pallet 3. When the pallet 3 is to be exchanged,the guide groove 14 of a pallet 3 is caused to slide in relation to theclamp guide plate 13.

A plurality of or, for example, four of pins 15 are secured to the clampbase 8 at the predetermined locations and bores 16 for positioning areprovided on the pallet 3 at the locations corresponding to the pins 15.When the pallet 3 is to be attached on the table 4, the piston 12 iscaused to be lowered at a specified location as shown in the left halfof FIG. 2 thereby lowering the pallet 3 and the bores 16 for positioningmay be held at such a condition as to engage with the pin 15. At thistime, the clamp guide plate 13 also urges the pallet 3 against the clampbase 8 by way of the guide groove 14.

If the pallet 3 is to be exchanged, the piston 12 is caused to ascendand the pallet is replaced while it is supported by the clamp guideplate 13.

A transmission device 17 includes a rack 18 secured to a member such asa saddle 6 as is stationary during exchanging the pallets, an idle gear20 in meshing engagement with the rack 18 and rotatably carried by ashaft 19 fixed to the clamp base 8 as shown in FIG. 2 and FIG. 4 and anoutput gear 21 in meshing engagement with the idle gear 20. The outputgear 21 is secured to an output shaft 22 rotatably and axially movablysupported by the clamp base 8. The output gear 21 is so constructed inorder for the axial movement of the output gear 21 in itself to causethe idle gear 20 also to axially move that side plates 21a are providedto sandwich the idle gear 20.

To the output shaft 22 is secured a catch plate 23 which is so shaped asto engage with a side groove 24 formed at the side surface of the pallet3. Vertical movement of the pallet will cause the output shaft 22 tomove vertically through engagement between the side groove 24 and thecatch plate 23.

When the pallet 3 is to be replaced, the pallet is in the liftedposition while the output shaft 22 and output gear 21 as well as theidle gear 20 are also in the lifted position. At such lifted positions,since the idle gear 20 is in meshing engagement with the rack 18, if theclamp base 8 constituting the table 4 for shifting the pallet 3 ismoved, this movement causes the output gear 21 or the output shaft 22 torotate.

In order to faciliate easy engagement of the catch plate 23 with theside groove 24 of the pallet 3 next to be attached even after the pallet3 has left the table, the spring 25 which is provided between the catchplate 23 and the clamp base 8 or the sleeve 8a attached to the clampbase 8 will cause the catch plate 23 or the output shaft 22 to be heldat the specified lifted position.

When the pallet 3 is lowered at the specified position and clamped onthe clamp base 8, the output shaft 22 is also lowered together with thecatch plate 23 and the output gear 21 as well as the idle gear 20 arealso lowered at the position shown by the phantom line. At this time,the idle gear 20 is in meshing engagement with the rack 18. In this way,even if the clamp base 8 is moved, the output shaft will not rotate.

To the output shaft 22 of the transmission apparatus is secured leverarm 27 constituting the speed-up device 26. A free end of the lever arm27 has a roller 29 slidable in a connecting groove 28 formed at one endportion of the pallet 3 and extending in the direction crossing thedirection of the movement of a pallet at the time of replacement of thepallet or the Y axis direction.

Replacement of the pallet takes place after the pallet 3 has beenclamped on the table 4 and the workpiece has been lowered to a specifiedposition. When the pallet is to be exchanged, the piston 12 is activatedto lift the pallet 3 so that engagement between the pin 15 and the bore16 for positioning may be released. At this time uplifting of the pallet3 causes the catch plate 23 to be correspondingly lifted and the leverarm 27 and the output gear 21 are also lifted so as to permit the idlegear 20 to engage with the rack 18. At this instance, the pallet 3 andthe clamp base 8 are located at the positions shown by the solid line inFIG. 1. At the time of exchanging the pallet the clamp base 8 is movedto the right side of FIG. 1 by rotation of the ball-screw 9 from theposition shown by the solid line.

As the clamp base 8 is shifted, the shaft 19 will be shiftedaccordingly, so that the idle gear 20 is caused to be rotatedanti-clockwise in FIG. 4 and rolled along the rack 1. Rotation of theidle gear 20 leads to rotation of the output gear 21 and the outputshaft 22 will be thereby rotated clockwise. Rotation of the output shaft22 is transmitted to the lever arm 27 of the speed-up device 26 in theform of clockwise rotation. The lever arm 27 is caused to move in therightward direction in FIG. 1 to the position shown by the phantom linein respect of the supporting position by the distance corresponding tothe movement of the clamp base 8 and during that movement, the lever arm27 is caused to be rotated by about 180 degrees at a speed-up rate inthe clockwise direction. Rotation of the lever arm 27 also causes, inaddition to displacement of the supporting position of the lever arm 27,the pallet 3 to be shifted rightwardly in FIG. 1 by the distanceequivalent to two times of the linear length of said lever arm. Thelength of the lever arm 27 may be so suitably selected that a slightshifting of the clamp base 8 permits the pallet 3 to be shifted to thepredetermined waiting position positioned completely outside of thetable.

It is to be seen from FIG. 1 that after the pallet loaded with themachined workpieces has been shifted to a first waiting position A, theroller 29 of the lever arm 27 is caused to move along the connectinggroove 28 of the pallet 3 currently placed at the first waiting positionA by shifting the table 4 or for example the saddle 6 in the directionof Y axis and then come out of the connecting groove, thereby releasingconnection between the lever arm 27 and the pallet 3. Further movementof the table 4 causes the roller 29 of the lever arm 29 to engage withthe connecting groove 28 of the pallet 3 loaded with the workpieces tobe machined which is waiting at a second waiting position B, so that thelever arm 27 and the pallet 3 may be coupled. After this coupling hastaken place, when the clamp base 8 is leftwardly moved as seen from FIG.1, the idle gear 20 will be rotated in the direction opposite to thearrow in FIG. 4 or clockwise and caused to roll along the rack 18. Thisrotation of the idle gear 20 causes the lever arm 27 to be rotated inthe anti-clockwise direction so that the pallet 3 may slide over theclamp base 8 and the clamp plate 13 may be fitted in the guide groove 14of the pallet 3. When the clamp base 8 has arrived at the specifiedposition, the piston 12 is activated so that the clamp plate 13 may belowered and the pallet 3 may be held with the pin 15 engaged with thebore 16 for positioning.

A modified embodiment as shown in FIG. 5 may be incorporated in thetransmission 17 and the speed-up device 26. In FIG. 5, the idle gear 20has been omitted and the output gear 21 may be engageable directly withthe rack 18. While in FIG. 1 the lever arm 27 has been used as a part ofthe speed-up device 26, in the embodiment shown in FIG. 5, the speed-updevice comprises a gear 30 fixed to the output shaft 22 and a rack 31adapted to mesh with the gear 30 and secured to the pallet 3. Speed-upfunction and stroke extending function may be attained by increasing thenumber of teeth of the gear 30 in relation to the output gear 21.

A further embodiment of the transmission device 17 and the speed-updevice 26 is as shown in FIG. 6 and FIG. 7. This embodiment comprisessprockets 33, 34 rotatably supported respectively on two shafts 32fixedly mounted to the clamp base 8 and a chain 35 wound around thesprockets 33, 34. A part of the chain 35 is fixed to the saddle 6. Atanother position of the chain 35 is secured an engaging member 36 suchas a chain plate having a recess, and a claw member 37 engageable withthe engaging member such as for example a plate member having aprojection insertable into the recess of the chain plate is fixed to thepallet 3.

When the workpiece or the workpieces on the pallet 3 are to be machined,the pallet 3 loaded with such workpieces is at the lowered position andsince the claw member 37 is disengaged from the engaging member 36, evenif the clamp base 8 is moved and the sprockets 33, 34 are rotated, thepallet 3 will not be affected at all.

When the pallet is to be exchanged, and the pallet 3 is lifted up, theclaw member 37 will come into engagement with the engaging member 36. Inthis condition, if the clamp base 8 is shifted, the sprockets 33. 34 arecaused to be shifted together with the clamp base 8. Since the chain 35is secured to the saddle 6, the sprockets 33, 34 are caused to berotated as the clamp base 8 is moved. The engaging member 36 of thechain 35 is caused to be shifted in the direction of movement of theclamp base 8 by the rate two times as high as the movement of the clampbase 8 or the combined movements of the linear movement of the sprockets33, 34 themselves and the rotational movement of the sprockets 33, 34.Since the engaging member 36 is connected to the pallet 3 by means ofthe claw member 37, the pallet 3 may be moved two times as fast as theclamp base 8. The movable range of the clamp base 8 should be soselected that the pallet 3 may be moved out of the clamp base to thewaiting position.

A still further embodiment as shown in FIG. 8 may be employed for thetransmission 17 and the speed-up device 26. In FIG. 8, rotation of theball-screw 9 is used to rotate sprockets 39, 40 through a chain 38 andthe rotation transmission such as belts and pulleys or gear trains, etc.are utilized as the transmission 17. The sprocket 40 is secured to theclamp base 8. To an output shaft 22 is secured a cam 42 such as acylindrical cam. A roller 43 or a cam follower for the cam 42 is fixedlymounted to the pallet 3 through a bracket 44. The speed-up device 26 ismade up of the cam 42 and the cam follower 43.

When the pallet 3 is lowered upon machining the workpieces, the camfollower 43 is moved out of the cam 42 and even if the ball-screw 9 isrotated, the pallet 3 will not be affected at all.

Upon exchanging the pallet, the pallet 3 is lifted up while at the sametime the cam follower 43 is raised to come into engagement with the camgroove of the cam 42. When the clamp base 8 is shifted, rotation of theball-screw 9 will be transmitted to the cam 42 by way of the outputshaft 22.. The shifting speed of the pallet 3 may be appropriatelyspeeded up in relation to the shifting speed of the clamp base 8 byselecting the number of teeth of the sprockets 39, 40 and the feed orpitch per revolution of the cam groove of the cylindrical cam 42 inaccordance with the rpm of the ball-screw 9 relative to a specifiedshifting amount of the clamp base 8. In addition, the shifting amount ofthe pallet 3 may be readily selected by switably selecting the length ofthe cam 42.

It is to be noted that compared to the embodiments shown in FIG. 5through FIG. 8 in which a manual or separate pallet shifting means isrequired for connecting the pallet loaded with the machined workpiecesand the pallet loaded with the workpieces still to be machined to thespeed-up device, the embodiment shown in FIG. 1 has such an advantage asmovement of the table may be utilized for exchanging and connecting thepallet.

What is claimed is:
 1. The combination of a machine tool, a plurality ofpallets and a pallet exchanging apparatus for the machine tool in whichone of said pallets loaded with machined workpieces and placed on atable of such machine tool is moved to a first waiting position andexchanged with another of said pallets with workpieces to be machinedwhich has been placed at a second waiting position, in which the tableof the machine tool comprises a clamp base for mounting thereon of oneof said pallets and a saddle on which the clamp base is mounted, theclamp base being movable on the saddle toward said first waitingposition, a transmission device is connected to the clamp base to outputrotational movement and a speed-up device is connected to saidtransmission device and adapted to provide said pallet loaded withmachined workpieces with linear movement toward said first waitingposition of higher speed and larger stroke than those of linear movementof said clamp base toward said first waiting position, said transmissiondevice comprising two sprockets rotatably supported on said clamp baseand said speed-up device comprising a chain wound around said sprockets,an engaging member fixed to a part of said chain, another part thereofbeing fixed to said saddle, and each of said pallets having fixedthereto a claw member engageable with said engaging member.
 2. A palletexchanging apparatus of claim 1, wherein said engaging member comprisesa chain plate with a recess and said claw member having a projectioninsertable into said recess of chain plate.